Add solution #974

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,057 LeetCode solutions in JavaScript
+# 1,058 LeetCode solutions in JavaScript
 
 [https://leetcode.com/](https://leetcode.com/)
 
@@ -782,6 +782,7 @@
 971|[Flip Binary Tree To Match Preorder Traversal](./solutions/0971-flip-binary-tree-to-match-preorder-traversal.js)|Medium|
 972|[Equal Rational Numbers](./solutions/0972-equal-rational-numbers.js)|Hard|
 973|[K Closest Points to Origin](./solutions/0973-k-closest-points-to-origin.js)|Medium|
+974|[Subarray Sums Divisible by K](./solutions/0974-subarray-sums-divisible-by-k.js)|Medium|
 976|[Largest Perimeter Triangle](./solutions/0976-largest-perimeter-triangle.js)|Easy|
 977|[Squares of a Sorted Array](./solutions/0977-squares-of-a-sorted-array.js)|Easy|
 985|[Sum of Even Numbers After Queries](./solutions/0985-sum-of-even-numbers-after-queries.js)|Easy|

solutions/0974-subarray-sums-divisible-by-k.js

@@ -0,0 +1,30 @@
+/**
+ * 974. Subarray Sums Divisible by K
+ * https://leetcode.com/problems/subarray-sums-divisible-by-k/
+ * Difficulty: Medium
+ *
+ * Given an integer array nums and an integer k, return the number of non-empty subarrays
+ * that have a sum divisible by k.
+ *
+ * A subarray is a contiguous part of an array.
+ */
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+var subarraysDivByK = function(nums, k) {
+  const remainderCount = new Map([[0, 1]]);
+  let sum = 0;
+  let result = 0;
+
+  for (const num of nums) {
+    sum += num;
+    const remainder = ((sum % k) + k) % k;
+    result += remainderCount.get(remainder) || 0;
+    remainderCount.set(remainder, (remainderCount.get(remainder) || 0) + 1);
+  }
+
+  return result;
+};